Hepatic cytochrome P-448 and epoxide hydrase: Enzymes of nuclear origin are immunochemically identical with those of microsomal origin

Nuclear and microsomal sources of hepatic cytochrome P-448 and epoxide hydrase were compared using antibodies made against the pure antigens isolated from rat liver microsomes. Both antigens were easily detected in detergent-solubilized nuclei and microsomes from rats using the Ouchterlony double-diffusion technique. Epoxide hydrase from either whole nuclei or nuclear envelope was immunochemically identical with the enzyme isolated from microsomes. Similarly, in rats pretreated with 3-methylcholanthrene, the cytochrome P-448 of nuclear origin was immunochemically indistinguishable from the enzyme derived from microsomes. These results establish the immunochemical identity of these hepatic nuclear and microsomal enzymes and provide a firm basis for applying the knowledge gained with the microsomal system of metabolism to the nuclear system.